<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .box1 {
            float: right;
            width: 0;
            height: 0;
            /* border-top: 100px solid transparent;
            border-right: 50px solid pink; */
            /* 简写 */
            border-color: transparent #fff transparent transparent;
            border-style: solid;
            border-width: 100px 50px 0 0;
        }

        .box {
            width: 700px;
            height: 100px;
            line-height: 100px;
            background-color: red;
            border: 1px solid red;
        }

        .box .box3 {
            float: left;
            width: 400px;
            height: 100px;
        }

        .box .box2 {
            text-align: center;
            float: left;
            width: 300px;
            height: 100px;
            background-color: #fff;
            text-decoration: line-through;
        }
    </style>
</head>

<body>
    <div class="box">
        <span class="box3">
            <div class="box1"></div>
        </span>
        <span class="box2">23234</span>
    </div>
</body>

</html>